This application, and the innovations and related subject matter disclosed herein, (collectively referred to as the “disclosure”) generally concern acoustic enclosures, and more particularly but not exclusively, enclosures suitable for headphones, with several vented enclosures for headphones being but particular examples incorporating disclosed innovations. Some disclosed enclosures define a waveguide for enhancing a frequency response, while also being configured to provide a thin enclosure. Some disclosed waveguides are further configured to passively attenuate environmental noise without substantially interfering with passive noise attenuation for headphones.
Audio headphones are worn on or over a user's ears. Audio headsets can have a headband for supporting a headphone in relation to a user's head. Often, such headsets include a pair of headphones, and the headband supports and separates the headphones from each other. Each headphone, in turn, can have one or more respective speaker transducers, sometimes referred to as “speakers” or “loudspeakers positioned within a housing. Generally speaking, the housing can define an acoustic enclosure for the speaker, providing the headphone with selected acoustic characteristics (e.g., a selected response at various audible frequencies, a degree of acceptable harmonic distortion, etc.). Headphones can also have ear pads, or cushions. Typically, ear cushions are provided to make wearing the headset comfortable, and to passively attenuate ambient noise.
As noted, ear pads for headphones or ear cushions for earphones can improve comfort for a user. Circumaural headphone ear pads and occluding earphone ear cushions, and to a smaller extent supraaural headphone ear pads and non-occluding earphone ear cushions, can also attenuate sound waves emitted by sources other than a corresponding headphone or earphone speaker transducer and can thus improve a user's listening experience in relation to sound emitted by the transducer. Such attenuation is sometimes referred to in the art as “passive” noise cancellation or attenuation.
In general, “passive” noise attenuation mechanically insulates a wearer's ear in relation to environmental sources of sound (generally referred to as “noise”). Although passive noise attenuation can improve a user's listening experience, it can be ineffective or less effective than desired for some frequency bands (e.g., below about 500 Hz).
A circumaural headphone, commonly referred to in the art as an “over-the-ear headphone,” has an ear pad configured to surround a user's outer ear and presses directly against the user's head at a position outwardly of the ear. By contrast, a supraaural headphone, commonly referred to in the art as an “on-ear headphone”, has an ear pad that rests on the wearer's outer ear.
Circumaural and supraaural headphones are contrasted with earphones that have small speaker enclosures typically worn in the user's outer ear, e.g., at an entrance to the wearer's ear canal. Some earphones do not have ear cushions. Other earphones have a cushioning member configured to enhance user comfort and/or to modify sound quality. Some cushioning members for earphones occlude a wearer's ear canal, and other cushioning members do not occlude the ear canal.
An enclosure for a speaker can define a first chamber and an opposed second chamber positioned opposite the first chamber relative to the speaker. Each chamber can be sealed or vented. Although a sealed chamber is not necessarily hermetically sealed, a sealed chamber inhibits or substantially prevents a flow of an ambient fluid, for example, air, across a boundary of the chamber as a diaphragm of the speaker vibrates to-and-fro emitting sound. By contrast, a vented chamber permits a flow of the ambient fluid across a boundary of the chamber. A given speaker combined with a vented chamber can provide different acoustic characteristics as compared to the same speaker combined with a sealed chamber.
For example, overall sound quality of a speaker combined with a sealed chamber, particularly in context of an enclosure for an earphone or headphone, is sometimes described as providing improved bass response, yet with a smaller soundstage and less fidelity compared to a vented (or “open”) enclosure. Such fidelity loss can arise, in part, from sympathetic acoustic and mechanical resonances within the chamber.
Nonetheless, conventional open enclosures do not lend themselves to passive acoustic attenuation, as external noise can “leak” through conventional vented chambers. As well, audio playback can “leak” through conventional open enclosures and disturb others near the listener.
An acoustic transmission line, or waveguide, can improve low-end frequency response of a vented enclosure. However, acoustic waveguides desirably provide a continuously expanding cross-sectional area (or nozzle). Conventional waveguides, therefore, have been large and bulky, and generally unsuitable for use in applications where small or otherwise diminutive enclosures are required or desired, such as in headphone or earphone applications, or in applications where aesthetic considerations are important.
Therefore, a need exists for improved loudspeaker enclosures. For example, enclosures providing strong bass response combined with high fidelity over desired audible frequencies are needed. A similar need exists for small or diminutive enclosures that allow users to enjoy accurate (e.g. low-distortion) reproduction of sound over extended low-frequencies. As well, a need remains for such enclosures that provide substantial passive noise attenuation. In addition, a need remains for such enclosures that are compatible with thin headphones and/or earphones.